Monoalphabetic Substitutions

This type of cipher involves substituting one letter of a plain text alphabet for each in the crypt alphabet.

For example:

    
Plain: abcgefg....
Crypt: TEGLSMN....

Whilst this code might seem a little harder to break then Caesar Shift, it’s still trivial to break.

Every language has characteristics. In english, there are only 2 letters that appear on thier own, ‘I’, and ‘a’, and there are a limited number of 2 letter words. Some 3 letter words are very common, ‘and’ and ‘the’ to name just two. More importantly, some letters are far more common then others. For example, ‘e’ is more common then ‘z’. Using a combination of these ‘rules’, it’s possible to decode text which was crypted using Monoalphabetic Substitution.